datafusion 4.0.0

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// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License.  You may obtain a copy of the License at
//
//   http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied.  See the License for the
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// under the License.

//! System variable provider

use crate::error::Result;
use crate::scalar::ScalarValue;
use crate::variable::VarProvider;

/// System variable
pub struct SystemVar {}

impl SystemVar {
    /// new system variable
    pub fn new() -> Self {
        Self {}
    }
}

impl VarProvider for SystemVar {
    /// get system variable value
    fn get_value(&self, var_names: Vec<String>) -> Result<ScalarValue> {
        let s = format!("{}-{}", "system-var".to_string(), var_names.concat());
        Ok(ScalarValue::Utf8(Some(s)))
    }
}

/// user defined variable
pub struct UserDefinedVar {}

impl UserDefinedVar {
    /// new user defined variable
    pub fn new() -> Self {
        Self {}
    }
}

impl VarProvider for UserDefinedVar {
    /// Get user defined variable value
    fn get_value(&self, var_names: Vec<String>) -> Result<ScalarValue> {
        let s = format!("{}-{}", "user-defined-var".to_string(), var_names.concat());
        Ok(ScalarValue::Utf8(Some(s)))
    }
}